RE: [PATCH 3/4] linux-user: fix TARGET_NSIG and _NSIG uses

[Taylor Simpson]

> -----Original Message-----
> From: Laurent Vivier <address@hidden>
> Sent: Saturday, February 1, 2020 6:28 AM
> To: address@hidden
> Cc: Josh Kunz <address@hidden>; address@hidden; Matus Kysel
> <address@hidden>; Aleksandar Markovic <aleksandar.markovic@rt-
> rk.com>; Marlies Ruck <address@hidden>; Laurent Vivier
> <address@hidden>; Peter Maydell <address@hidden>; Taylor
> Simpson <address@hidden>; Riku Voipio <address@hidden>
> Subject: [PATCH 3/4] linux-user: fix TARGET_NSIG and _NSIG uses
>
> Valid signal numbers are between 1 (SIGHUP) and SIGRTMAX.
>
> System includes define _NSIG to SIGRTMAX + 1, but QEMU (like kernel)
> defines TARGET_NSIG to TARGET_SIGRTMAX.
>
> Fix all the checks involving the signal range.
>
> Signed-off-by: Laurent Vivier <address@hidden>
> ---
>  linux-user/signal.c | 51 ++++++++++++++++++++++++++++++++-------------
>  1 file changed, 37 insertions(+), 14 deletions(-)
>
> diff --git a/linux-user/signal.c b/linux-user/signal.c index
> f42a2e1a82a5..3491f0a7ecb1 100644
> --- a/linux-user/signal.c
> +++ b/linux-user/signal.c
> @@ -30,6 +30,15 @@ static struct target_sigaction
> sigact_table[TARGET_NSIG];  static void host_signal_handler(int
> host_signum, siginfo_t *info,
>                                  void *puc);
>
> +
> +/*
> + * System includes define _NSIG as SIGRTMAX + 1,
> + * but qemu (like the kernel) defines TARGET_NSIG as TARGET_SIGRTMAX
> + * and the first signal is SIGHUP defined as 1
> + * Signal number 0 is reserved for use as kill(pid, 0), to test whether
> + * a process exists without sending it a signal.
> + */
> +QEMU_BUILD_BUG_ON(__SIGRTMAX + 1 != _NSIG);
>  static uint8_t host_to_target_signal_table[_NSIG] = {
>      [SIGHUP] = TARGET_SIGHUP,
>      [SIGINT] = TARGET_SIGINT,
> @@ -67,19 +76,24 @@ static uint8_t host_to_target_signal_table[_NSIG] = {
>      [SIGSYS] = TARGET_SIGSYS,
>      /* next signals stay the same */
>  };
> -static uint8_t target_to_host_signal_table[_NSIG];
>
> +static uint8_t target_to_host_signal_table[TARGET_NSIG + 1];
> +
> +/* valid sig is between 1 and _NSIG - 1 */
>  int host_to_target_signal(int sig)
>  {
> -    if (sig < 0 || sig >= _NSIG)
> +    if (sig < 1 || sig >= _NSIG) {
>          return sig;
> +    }
>      return host_to_target_signal_table[sig];  }
>
> +/* valid sig is between 1 and TARGET_NSIG */
>  int target_to_host_signal(int sig)
>  {
> -    if (sig < 0 || sig >= _NSIG)
> +    if (sig < 1 || sig > TARGET_NSIG) {
>          return sig;
> +    }
>      return target_to_host_signal_table[sig];  }
>
> @@ -100,11 +114,15 @@ static inline int target_sigismember(const
> target_sigset_t *set, int signum)  void
> host_to_target_sigset_internal(target_sigset_t *d,
>                                      const sigset_t *s)  {
> -    int i;
> +    int i, j;
>      target_sigemptyset(d);
> -    for (i = 1; i <= TARGET_NSIG; i++) {
> +    for (i = 1; i < _NSIG; i++) {
> +        j = host_to_target_signal(i);

More descriptive name - target_sig

> +        if (j < 1 || j > TARGET_NSIG) {
> +            continue;
> +        }
>          if (sigismember(s, i)) {
> -            target_sigaddset(d, host_to_target_signal(i));
> +            target_sigaddset(d, j);
>          }
>      }
>  }
> @@ -122,11 +140,15 @@ void host_to_target_sigset(target_sigset_t *d,
> const sigset_t *s)  void target_to_host_sigset_internal(sigset_t *d,
>                                      const target_sigset_t *s)  {
> -    int i;
> +    int i, j;
>      sigemptyset(d);
>      for (i = 1; i <= TARGET_NSIG; i++) {
> +        j = target_to_host_signal(i);

More descriptive name - host_sig

> +        if (j < 1 || j >= _NSIG) {
> +            continue;
> +        }
>          if (target_sigismember(s, i)) {
> -            sigaddset(d, target_to_host_signal(i));
> +            sigaddset(d, j);
>          }
>      }
>  }
> @@ -488,13 +510,14 @@ static void signal_table_init(void)
>      host_to_target_signal_table[__SIGRTMAX] = __SIGRTMIN;
>
>      /* generate signal conversion tables */
> -    for(i = 1; i < _NSIG; i++) {
> -        if (host_to_target_signal_table[i] == 0)
> +    for (i = 1; i < _NSIG; i++) {
> +        if (host_to_target_signal_table[i] == 0) {
>              host_to_target_signal_table[i] = i;
> -    }
> -    for(i = 1; i < _NSIG; i++) {
> +        }
>          j = host_to_target_signal_table[i];

More descriptive name - target_sig

> -        target_to_host_signal_table[j] = i;
> +        if (j <= TARGET_NSIG) {
> +            target_to_host_signal_table[j] = i;
> +        }
>      }
>  }
>
> @@ -517,7 +540,7 @@ void signal_init(void)
>      act.sa_sigaction = host_signal_handler;
>      for(i = 1; i <= TARGET_NSIG; i++) {  #ifdef TARGET_GPROF
> -        if (i == SIGPROF) {
> +        if (i == TARGET_SIGPROF) {
>              continue;
>          }
>  #endif
> --
> 2.24.1
>